CHICAGO — Ocular venous air embolism, a very rare complication of vitrectomy, is almost always fatal, yet some retina specialists have not heard of it. The complication can kill in less than a minute, said Robert Morris, MD, from Retina Specialists of Alabama and the University of Alabama at Birmingham. "Any vitrectomy that uses air infusion may result in ocular venous air embolism if insidious slippage of an infusion cannula during vitrectomy causes suprachoroidal infusion of pressurized air," he explained during the late-breaker session here at the American Society of Retina Specialists (ASRS) 2019 Annual Meeting. "Resultant tearing of the vortex veins can allow silent entrainment of suprachoroidal air into the systemic venous circulation at a rate that is usually fatal unless promptly detected," he added. In 2017, Morris and his team surveyed a random sampling of 30 ASRS members and found that 80% were not aware of the potential complication. There had been sporadic reports of the complication after the first case was reported in 2005, but he suspects that the majority of retina specialists have heard about it since, he told Medscape Medical News. A review of the complication by Morris and his colleagues was featured on the cover of the March/April issue of the Journal of VitreoRetinal Diseases (2019;2:99-106). The team searched the literature and other sources for suspected cases of air embolism during vitrectomy and confirmed that nine of the 13 cases reported since 2005 were fatal (69%); eight of those nine deaths occurred the day of the surgery. Gone in the Blink of an Eye Early skepticism about the complication — defined as "a precipitous drop in end-tidal CO₂, a choroidal detachment, or a choroidal wound followed by signs of impending or actual cardiovascular collapse during vitrectomy air infusion"— was understandable, Morris said. "It was difficult to believe that air could enter the heart from the eye so quickly through small veins," he explained. It was also something physicians did not want to think about. And because "you have to see it to believe it sometimes," the team included a simulation video in the supplemental material for their cover feature. The most important aspect of prevention, after awareness, is to take a time-out during the vitrectomy to confirm the infusion before going to air. "It could save a life," he said. About 85% of all retinal specialists are now well aware of ocular venous air embolism and the circumstances under which it could happen, said Timothy Murray, MD, president-elect of ASRS. "I think there's a huge broadened understanding of this because of the work that Dr Morris and others have done," he added. However, he emphasized, most cannula displacements are not life-threatening events and the circumstances need to be fairly unique. "It's an incredibly rare event," but preventable "in the majority of cases," he emphasized. Reconfirm the cannula in the intravitreal space before you go to air or gas exchange. Prevention starts with knowing where the infusion cannula is when you transition from fluid to air or gas, he said. "We talk about that all the time," Murray said. "When you put the cannula in, even before you begin fluid infusion, we teach that you confirm that the cannula is in the intravitreal space." Morris is suggesting that "you reconfirm the cannula in the intravitreal space before you go to air or gas exchange. I think that's totally reasonable," he added. Ophthalmology residents and fellows definitely need to be aware of this potential complication, said Dilraj Grewal, MD, from the Duke Eye Center in Durham, North Carolina. And "our anesthesia colleagues, including certified registered nurse anesthetists, should be aware of this while monitoring end-tidal CO₂ during retinal surgeries," he told Medscape Medical News. Source
